Unit 3 Oceanography Section 3 Currents Waves and

Unit 3 – Oceanography Section 3: Currents, Waves, and Tides Earth Science Mr. Margetan

Ocean Currents • Surface Currents – Movement of water on the surface, primarily caused by winds

Ocean Currents • Longshore Currents – Currents which run parallel to the shoreline due to energy released from waves

Ocean Currents • Upwelling Currents – Occur when wind moves seawater at the surface and new water from below replaces it

Critical Thinking #1 • How might upwelling currents be beneficial to life in the ocean? Explain.

Ocean Currents • Deep Currents – Move slowly beneath surface, primarily caused by differing water densities

Critical Thinking #2 • What processes might cause changes in density that form deep ocean currents?

Ocean Currents • Global Conveyor Belt – A connected deep ocean current that circles the entire planet

Waves • Waves – Up and down, circular movement of energy in water – Caused primarily by wind – Also, disturbances in the ocean, earthquakes

Critical Thinking #3 • How are ocean waves similar to seismic waves? How are they different?

Factors Influencing Wave Size • Strength of Wind – Speed wind is blowing • Fetch – Distance wind is blowing • Duration – Length wind is blowing

Parts of a Wave • Crest – Highest point on a wave • Trough – Lowest point on a wave • Wavelength – Horizontal distance from crest to crest • Wave Height – Vertical distance from crest to trough

How do Waves Break? • Waves begin to change shape at a depth ½ its wavelength • Waves break at a depth of 1. 3 x its wave height

Critical Thinking #4 • Considering how waves break, how might the shape of the ocean floor influence the shape of waves?

Types of Breakers • Surging Breakers – Waves roll into the shore, occurs at steep beaches • Plunging Breakers – Waves curl and break, occurs at moderate slope beaches • Spilling Breakers – Waves break far from shore, occurs at gentle slope beaches

Tides • Tides – Daily changes in the level of the ocean surface • 2 high tides and 2 low tides each day – caused by gravitational pull of primarily the moon, but also the sun

High Tides and Low Tides • High (Flood) Tides – Occur on side of Earth facing and opposite the moon, due to both gravity facing and centrifugal force opposite • Low (Ebb) Tides – Occur on sides halfway between the moon

Spring Tides and Neap Tides • Spring Tides = Highest and lowest tides, when moon and sun align • Neap Tides = Small tidal range, when moon and sun are perpendicular

Critical Thinking #5 • Why are spring tides stronger than neap tides? Explain.